The hydrogen economy is a delivering energy system by using hydrogen. The hydrogen can function as an energy storage medium, and it is generated by renewable energy and then stored until a fuel cell converts it back to electricity, which be able to replace the current petroleum economic system. The renewable energy is, for instance, electrolysis of water by using solar power, wind power, tidal power hydro power, or geothermal power. The electrochemical energy conversion devices such as fuel cells, electrolysers, solar hydrogen generators, or electrochemical sensors have reached to commercialization stage, but high cost and limited amount Pt catalyst hinder the development in acidic media. To overcome this issue, the Pt free catalyst is alternative. However, the energy conversion efficiency of the Pt free catalyst is too low due to the slower kinetics thereof in alkaline media. Therefore, the enhancement of the electrochemical reaction rate of the Pt free catalyst becomes very important.
One of the key challenges of the development of fuel cells, electrolysers, solar hydrogen generators, and electrochemical sensors in alkaline media is an electrode reaction for hydrogen. The hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) have faster reaction kinetics in acidic media. However, the HOR and HER have slower reaction kinetics in alkaline media.
Therefore, the development of high activity catalyst for hydrogen oxidation reaction and hydrogen evolution reaction is a top priority for fuel cells, electrolysers, solar hydrogen generators, and electrochemical sensors in alkaline media.